My first observation was the 23/33 combo. That's a bit stiff in the rear. A more common setup is 23/30 or 23/31
If it wants to swap ends braking in a straight line, it sounds like too much rear brake. But not so much rear brake that you are locking up the rears? You say you've got Carrera calipers all around. Do you still have the rear pressure reduction valve in place? If not, the Carrera calipers have a hyd. bias that's pretty aggressive at 1.3-something (going by memory here) which is pretty aggressive, especially if you don't have a limited slip to help stabilize the car under braking.
I just don't like the Carrera brake balance even when the pressure limiting valve is in place because it doesn't produce good feel. I've fiddled with the brake balance by swapping some different front brakes and I noticed a huge difference when going slightly larger in the front (VCI front Brembo kit with basic small 4 piston caliper and 299x28mm rotors) and removing the pressure reduction valve.
I don't think the 17s are a must. 225 and 245 is a pretty decent combo for a Carrera and as long as you've got good wheel widths (8 in front, 9 in rear would be ideal) you should have a well balanced car with a good grip threshold.
I had my '87 Carrera tuned sort of similar to yours.
23/31 torsions
TRG (Tarett rip-off copy) adjustable rear bar set around mid stiff, fixed stock front sway bar
Koni single adjustable shocks set almost fully firm (rebound)
Small Brembo brakes
16x8/9 BBS RS with 14mm rear spacers added and 225/50, 245/45 Victoracers
No limited slip
Corner weights with equal cross weighting
Not super light weight- around 2650 with me in the car
Aggressive/track-oriented alignment but not crazy. A teensy bit of toe out in the front, decent negative front camber, plenty of rear neg camber (I notice you have less in the rear compared to front- I would try for more rear on your car) plenty of rear toe-in
https://www.youtube.com/watch?v=--Br8BWBTmE
That footage isn't to show how fast I was. 1:22 is a decent lap. But not earth shattering. Heck, I go 4 seconds faster in my racecar. But I think it's a decent example of a mildly modified car getting around there fairly quickly with good balance.
Note the ride height of my car. Not real low. If you don't have the proper geometry up front, that very low ride height can induce a lot of bump steer- toe change due to suspension travel. The buttmunch chasing me in the silver 911 would constantly poke fun at me about my "Ranchero" ride height. Ha ha. Who's laughing when he's sawing at the wheel like a maniac in his very low "stock" car trying to catch me while I just steer like a normal person.
I think you are OK with the BFG R1. They are very comparable to the Hoosier R6. Also, if your car is light, you can easily get away with using the BFG R1-S. I ran the S in hellacious heat 40 min race on my '79 racecar and they did not "go-off" on me. I was shocked to say the least.